<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<input type="button" value="上一页"  onclick="back()"/>
		<input type="button" value="下一页"  onclick="next()"/>
		<img src="1.jpg" id="d1"/>
	</head>
	<body>
		<script>
			var back = function(){
				d1.src="images/2.jpg";
			};
		</script>
	</body>
</html>
